The present invention relates to load carrying vehicles in general and more in particular to a vehicle capable of stepping its wheels so as to avoid bearing on fragile edges of objects in its path.
Huge pipe sections used in the likes of large water projects measuring 250 inches or so in diameter and weighing on the order of 200 tons must be transported to their permanent site. It has been the practice to use pipe laying vehicles for this purpose. Such a vehicle drives through the pipe and lifts the pipe from within it on a main frame or carriage of the vehicle. The carriage is between wheeled ends of the vehicle. The vehicle then transports the pipe to its desired location. The lips or edges of these pipes, as huge as the pipes are, are comparatively fragile and can fail if driven over by the tires of a pipe transporting vehicle. Accordingly it has been the practice to provide a stepper at one end of the vehicle to step the wheels into the pipe and out of the pipe without encountering the lips of the pipe. Such a construction is shown in U.S. Pat. No. 2,954,136 to Butler, Jobe, and Domis.
The stepper assemblies of previous pipe transporting vehicles have inadequate tire-to-ground bearing to support payloads on the order of 220 tons.
Previous vehicles have had difficulty in handling road imposed loads and this difficulty has resulted in comparatively low vehicle speeds. For example, galloping from resonance would occur at medium vehicle speeds. Additionally, shock resulting from movement of massive structure in response to irregularities in the path of the vehicle may severely load the structure and the pipe payload.